Jam-tolerant linear control motor for hydraulic actuator valve

ABSTRACT

According to one embodiment, a linear control motor includes a first permanent magnet, a coil, a first magnetic material, a shaft, and a first non-magnetic material. The first non-magnetic material is disposed between at least one of the movable components and at least one of the static components and operable to prevent physical contact between at least one of the movable components and at least one of the static components.

TECHNICAL FIELD

This invention relates generally to rotorcraft flight control systems,and more particularly, to a jam-tolerant linear control motor for ahydraulic actuator valve.

BACKGROUND

A rotorcraft may include one or more rotor systems. One example of arotorcraft rotor system is a main rotor system. A main rotor system maygenerate aerodynamic lift to support the weight of the rotorcraft inflight and thrust to counteract aerodynamic drag and move the rotorcraftin forward flight. Another example of a rotorcraft rotor system is atail rotor system. A tail rotor system may generate thrust in the samedirection as the main rotor system's rotation to counter the torqueeffect created by the main rotor system. A rotor system may include oneor more devices to rotate, deflect, and/or adjust rotor blades.

SUMMARY

Particular embodiments of the present disclosure may provide one or moretechnical advantages. A technical advantage of one embodiment mayinclude the capability to reduce magnetic seizing in a control motor fora rotorcraft blade actuator. A technical advantage of one embodiment mayinclude the capability to detect bearing failures in a control motorprior to catastrophic failure. A technical advantage of one embodimentmay include the capability to reduce failures in joints that convertrotary motion into linear motion.

Certain embodiments of the present disclosure may include some, all, ornone of the above advantages. One or more other technical advantages maybe readily apparent to those skilled in the art from the figures,descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present invention andthe features and advantages thereof, reference is made to the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A shows a rotorcraft according to one example configuration;

FIG. 1B shows the rotor system and blades of FIG. 1A according to oneexample configuration;

FIG. 2A shows an example redundant control system for a fixed-wingaircraft;

FIG. 2B shows an example redundant control system for a rotorcraft suchas the rotorcraft of FIG. 1A;

FIG. 3 shows a cross-section view of a linear control motor according toone example embodiment;

FIG. 4 shows a cross-section view of a linear control motor according toanother example embodiment;

FIG. 5 shows a cross-section view of a linear control motor according toyet another example embodiment;

FIG. 6 shows a cross-section view of a linear control motor according toyet another example embodiment;

FIG. 7A shows a control system featuring a rotary control motor, ahydraulic system, and an actuator according to one example embodiment;

FIG. 7B shows side view of a joint associated with the control system ofFIG. 7A;

FIGS. 7C-7F shows a cross-section views of the joint of FIG. 7B;

FIGS. 8A and 8B show cross-section views of a rotary control motoraccording to one example embodiment;

FIGS. 9A and 9B show cross-section views of a rotary control motoraccording to another example embodiment;

FIGS. 10A and 10B show cross-section views of a rotary control motoraccording to yet another example embodiment;

FIGS. 11A and 11B show cross-section views of a rotary control motoraccording to yet another example embodiment; and

FIGS. 12A, 12B, and 12C show cross-section views of a rotary controlmotor according to yet another example embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a rotorcraft 100 according to one example configuration.Rotorcraft 100 features a rotor system 110, blades 120, a fuselage 130,a landing gear 140, and an empennage 150. Rotor system 110 may rotateblades 120. Rotor system 110 may include a control system forselectively controlling the pitch of each blade 120 in order toselectively control direction, thrust, and lift of rotorcraft 100.Fuselage 130 represents the body of rotorcraft 100 and may be coupled torotor system 110 such that rotor system 110 and blades 120 may movefuselage 130 through the air. Landing gear 140 supports rotorcraft 100when rotorcraft 100 is landing and/or when rotorcraft 100 is at rest onthe ground. Empennage 150 represents the tail section of the aircraftand features components of a rotor system 110 and blades 120′. Blades120′ may provide thrust in the same direction as the rotation of blades120 so as to counter the torque effect created by rotor system 110 andblades 120. Teachings of certain embodiments relating to rotor systemsdescribed herein may apply to rotor system 110 and/or other rotorsystems, such as other tilt rotor and helicopter rotor systems. Itshould also be appreciated that teachings from rotorcraft 100 may applyto aircraft other than rotorcraft, such as airplanes and unmannedaircraft, to name a few examples.

FIG. 1B shows rotor system 110 and blades 120 of FIG. 1A according toone example configuration. In the example configuration of FIG. 1B,rotor system 110 features a power train 112, a hub 114, a swashplate116, and pitch links 118. In some examples, rotor system 110 may includemore or fewer components. For example, FIG. 1B does not show componentssuch as a gearbox, a swash plate, drive links, drive levers, and othercomponents that may be incorporated.

Power train 112 features a power source 112 a and a drive shaft 112 b.Power source 112 a, drive shaft 112 b, and hub 114 are mechanicalcomponents for transmitting torque and/or rotation. Power train 112 mayinclude a variety of components, including an engine, a transmission,and differentials. In operation, drive shaft 112 b receives torque orrotational energy from power source 112 a and rotates hub 114. Rotationof rotor hub 114 causes blades 120 to rotate about drive shaft 112 b.

Swashplate 116 translates rotorcraft flight control input into motion ofblades 120. Because blades 120 are typically spinning when therotorcraft is in flight, swashplate 116 may transmit flight controlinput from the non-rotating fuselage to the hub 114, blades 120, and/orcomponents coupling hub 114 to blades 120 (e.g., grips and pitch horns).References in this description to coupling between a pitch link and ahub may also include, but are not limited to, coupling between a pitchlink and a blade or components coupling a hub to a blade.

In some examples, swashplate 116 may include a non-rotating swashplatering 116 a and a rotating swashplate ring 116 b. Non-rotating swashplatering 116 a does not rotate with drive shaft 112 b, whereas rotatingswashplate ring 116 b does rotate with drive shaft 112 b. In the exampleof FIG. 1B, pitch links 118 connect rotating swashplate ring 116 b toblades 120.

In operation, according to one example embodiment, translating thenon-rotating swashplate ring 116 a along the axis of drive shaft 112 bcauses the pitch links 118 to move up or down. This changes the pitchangle of all blades 120 equally, increasing or decreasing the thrust ofthe rotor and causing the aircraft to ascend or descend. Tilting thenon-rotating swashplate ring 116 a causes the rotating swashplate 116 bto tilt, moving the pitch links 118 up and down cyclically as theyrotate with the drive shaft. This tilts the thrust vector of the rotor,causing rotorcraft 100 to translate horizontally following the directionthe swashplate is tilted.

Redundant flight control components may be provided to improve safety ofrotorcraft 100. For example, the rotor system 110 of FIG. 1B may includeredundant components for controlling deflection and position of blades120. However, providing flight control redundancy in a rotorcraft, suchas the example rotorcraft 100, may be somewhat more difficult thanproviding flight control redundancy in a fixed-wing aircraft.

FIGS. 2A and 2B show example redundant control systems for a fixed-wingaircraft and for a rotorcraft. The example of FIG. 2A represents aredundant control system for a fixed-wing aircraft. In the example ofFIG. 2A, two redundant flight control devices 210′ and 210″ areprovided. Each flight control device is controlled by two redundantactuators 220 (for a total of four actuators). The four actuators 220are controlled by three redundant hydraulic systems 230.

The example of FIG. 2B, on the other hand, represents a redundantcontrol system for a rotorcraft. Unlike the example of FIG. 2A, thesystem of FIG. 2B includes a single flight control device 210. In thisexample embodiment, flight control device 210 may represent a rotorcraftflight control component, such as swashplate 116, that does not have aredundant counterpart installed on rotorcraft 100.

Teachings of certain embodiments recognize that providing redundancy inthe system of FIG. 2B is therefore more important when only a singleflight control device 210 is provided. In the example of FIG. 2B, tworedundant actuators 220 are provided to position flight control device210. The two redundant actuators 220 are controlled by hydraulic systems230, hydraulic systems 232, and a switching valve 234.

In one example embodiment, actuators 220 and hydraulic systems 230 mayrepresent the dual motor dual concentric valve actuator 101 describedand/or suggested by U.S. Pat. No. 7,828,245, issued on Nov. 9, 2010. Forexample, actuator 220 may represent the parallel dual piston actuator111 of U.S. Pat. No. 7,828,245, and hydraulic system 230 may representdual concentric valve 102, which is controlled by motor 119. U.S. Pat.No. 7,828,245 is hereby incorporated by reference in its entirety.

Although the example of FIG. 2B features redundant actuators 220, FIG.2B shows the redundant actuators 220 coupled together in series. Thus,in this example, failure by one actuator 220 could cause the redundantactuator 220 to fail. For example, if one actuator 220 locks in a fixedposition, the locked actuator 220 could prevent the redundant 220 frommoving.

Accordingly, teachings of certain embodiments recognize that performanceof actuator 220 may be critical to flight safety. As will be explainedin greater detail below, teachings of certain embodiments recognize thecapability to prevent failures of actuator 220. In particular, teachingsof certain embodiments recognize the capability to prevent failures ofactuator 220 by preventing failures of the control motor that controlshydraulic fluid flow to actuator 220.

FIG. 3 shows a cross-section view of a control motor 300 according toone example embodiment. In the example of FIG. 3, control motor 300 iscoupled to hydraulic system 230. In some embodiments, hydraulic system230 may represent dual concentric valve 102 of U.S. Pat. No. 7,828,245,and control motor 300 may represent an example configuration of themotor 119 of U.S. Pat. No. 7,828,245. In the example of FIG. 3,hydraulic system 230 is shown as a simplified hydraulic valve featuringa servo valve and a spool extending through the servo valve.

In the example of FIG. 3, control motor 300 features a magnet 310, acoil 320, magnetic material 330, non-magnetic material 340, and a shaft350. In this example, magnet 310 and magnetic material 330 may beconsidered static components, and coil 320 may be considered a movablecomponent. A movable component may represent any component that movesrelative to a static component. A static component may be consideredfixed relative to movable components, although in reality staticcomponents themselves may be subject to some movement.

In operation, magnet 310 generates magnetic flux along magnetic fluxpath 315. Magnetic material 330 is disposed at least partially inmagnetic flux path 315 and may reduce loss of flux along magnetic fluxpath 315. Coil 320 selectively adds magnetic flux to and/or subtractsmagnetic flux from magnetic flux path 315. Adding or subtractingmagnetic flux may cause coil 320 to move linearly within control motor300. Non-magnetic material 340 and shaft 350 couple coil 320 to thespool of hydraulic system 230 such that the spool of hydraulic system230 moves in response variations in magnetic flux in magnetic flux path315.

Magnet 310 may represent any material or object that is operable toproduce a magnetic field and/or generate a magnetic flux path. Examplesof magnet 310 may include a permanent magnet or an electromagnetic. Coil320 may represent any material or object that is operable to add orremove flux to or from a magnetic flux path. In some embodiments, coil320 resembles a series of loops of conductive material, such as solidcopper wire. Magnetic material 330 may represent any material or objectthat is attracted to (or repulsed by) a magnet. In some embodiments,magnetic material 330 may include ferromagnetic materials, such as iron,nickel, cobalt, rare earth magnets, and some alloys. Non-magneticmaterial 340 may represent material is not attracted to (or repulsed by)a magnet. Examples of non-magnetic material 340 may include somerubbers, plastics, and wood.

In the example of FIG. 3, coil 320 is disposed within control motor 300adjacent to magnetic material 330. During normal operation, coil 320 maybe free to move linearly within control motor 300 adjacent to magneticmaterial 330. A failure can occur, however, if coil 320 magneticallyseizes to magnetic material 330. In this failure mode, coil 320 becomesfixed and prevents shaft 350 from moving the spool of hydraulic system230, which may result in a failure of the actuator 220 coupled tohydraulic system 230. Accordingly, as will be explained in greaterdetail below, teachings of certain embodiments recognize the capabilityto prevent failures of actuator 220 and hydraulic system 230 bypreventing magnetic seizing of the control motor.

FIG. 4 shows a cross-section view of a control motor 400 according toone example embodiment. In the example of FIG. 4, control motor 400 iscoupled to hydraulic system 230. In some embodiments, hydraulic system230 may represent dual concentric valve 102 of U.S. Pat. No. 7,828,245,and control motor 400 may represent an example configuration of themotor 119 of U.S. Pat. No. 7,828,245. In the example of FIG. 4,hydraulic system 230 is shown as a simplified hydraulic valve featuringa servo valve and a spool extending through the servo valve.

In the example of FIG. 4, control motor 400 features a magnet 410, acoil 420, magnetic material 430, nonmagnetic material 440, and a shaft450. In some embodiments, some of these components may resemble themagnet 310, coil 320, magnetic material 330, non-magnetic material 340,and shaft 350 of control motor 300. For instance, similar to the magnet310 of control motor 300, magnet 410 generates magnetic flux alongmagnetic flux path 415. Unlike control motor 300, however, control motor400 features additional non-magnetic material 440 separating coil 420from magnetic material 430. Teachings of certain embodiments recognizethat the non-magnetic material 440 may prevent coil 420 from seizing tomagnetic material 430 by preventing physical contact between coil 420and the magnetic material 430.

In the example of FIG. 4, control motor 400 also features springs 445that may allow the non-magnetic material 440 to move somewhat relativeto coil 420 and/or magnetic material 430. Teachings of certainembodiments recognize that allowing some movement by the non-magneticmaterial 440 separating coil 420 from magnetic material 430 may furtherreduce seizing by control motor 400.

FIG. 5 shows a cross-section view of a control motor 500 according toone example embodiment. Control motor 500 may represent an alternativeconfiguration of the control motor 300 of FIG. 3. In the example of FIG.5, control motor 500 is coupled to hydraulic system 230. In someembodiments, hydraulic system 230 may represent dual concentric valve102 of U.S. Pat. No. 7,828,245, and control motor 500 may represent anexample configuration of the motor 119 of U.S. Pat. No. 7,828,245. Inthe example of FIG. 5, hydraulic system 230 is shown as a simplifiedhydraulic valve featuring a servo valve and a spool extending throughthe servo valve.

In the example of FIG. 5, control motor 500 features magnets 510, a coil520, magnetic material 530, a magnetic armature 535, and a shaft 550. Inthis example, magnets 510, coil 520, and magnetic material 530 may beconsidered static components, and armature 535 may be considered amovable component.

In operation, magnets 510 generate magnetic flux along magnetic fluxpaths 515. Magnetic material 530 is disposed at least partially in amagnetic flux path 515 and may reduce loss of flux along magnetic fluxpath 515. Coil 520 selectively adds magnetic flux to and/or subtractsmagnetic flux from magnetic flux paths 515. Magnetic armature 535 isalso at least partially disposed in the magnetic flux paths 515. Addingor subtracting magnetic flux may cause magnetic armature 535 to movelinearly within control motor 500. Shaft 550 couples magnetic armature535 to the spool of hydraulic system 230 such that the spool ofhydraulic system 230 moves in response to variations in magnetic flux inmagnetic flux paths 515.

In the example of FIG. 5, magnets 510 generate two magnetic flux paths515. In this example, magnetic flux paths 515 flow in oppositedirections such that the first magnetic flux path 515 is operable tomove magnetic armature 535 in a first direction and the second magneticflux path 515 is operable to move magnetic armature 535 in an oppositesecond direction. If the magnitude of the two magnetic flux paths 515 isequal, the two magnetic flux paths may substantially maintain magneticarmature 535 in equilibrium. If the magnitude of the two magnetic fluxpaths 515 is not equal, then equilibrium is not maintained, and magneticarmature 535 may move linearly as a result of the difference in flux inthe two magnetic flux paths.

Magnet 510 may represent any material or object that is operable toproduce a magnetic field and/or generate a magnetic flux path. Examplesof magnet 510 may include a permanent magnet or an electromagnetic. Coil520 may represent any material or object that is operable to add orremove flux to or from a magnetic flux path. In some embodiments, coil520 resembles a series of loops of conductive material, such as solidcopper wire. Magnetic material 530 and magnetic armature 535 mayrepresent any material or object that is attracted to (or repulsed by) amagnet. In some embodiments, magnetic material 530 and magnetic armature535 may include ferromagnetic materials, such as iron, nickel, cobalt,rare earth magnets, and some alloys.

In the example of FIG. 5, magnetic armature 535 is disposed withincontrol motor 500 adjacent to magnets 510 and/or magnetic material 530.During normal operation, magnetic armature 535 may be free to movelinearly within control motor 500 adjacent to magnets 510 and/ormagnetic material 530. A failure can occur, however, if magneticarmature 535 magnetically seizes to magnets 510 and/or magnetic material530. In this failure mode, magnetic armature 535 becomes fixed andprevents shaft 550 from moving the spool of hydraulic system 230, whichmay result in a failure of the actuator 220 coupled to hydraulic system230. Accordingly, as will be explained in greater detail below,teachings of certain embodiments recognize the capability to preventfailures of actuator 220 and hydraulic system 230 by preventing magneticseizing of the control motor.

FIG. 6 shows a cross-section view of a control motor 600 according toone example embodiment. In the example of FIG. 6, control motor 600 iscoupled to hydraulic system 230. In some embodiments, hydraulic system230 may represent dual concentric valve 102 of U.S. Pat. No. 7,828,245,and control motor 600 may represent an example configuration of themotor 119 of U.S. Pat. No. 7,828,245. In the example of FIG. 6,hydraulic system 230 is shown as a simplified hydraulic valve featuringa servo valve and a spool extending through the servo valve.

In the example of FIG. 6, control motor 600 features a magnet 610, acoil 620, magnetic material 630, magnetic armature 635, non-magneticmaterial 640, and a shaft 650. In some embodiments, some of thesecomponents may resemble the magnet 510, coil 520, magnetic material 530,magnetic armature 535, non-magnetic material 540, and shaft 550 ofcontrol motor 500. For instance, similar to the magnet 510 of controlmotor 500, magnet 610 generates magnetic flux along magnetic flux path615. Unlike control motor 500, however, control motor 600 featuresadditional non-magnetic material 640 separating magnetic armature 635from magnets 610 and magnetic material 630. Teachings of certainembodiments recognize that the non-magnetic material 640 may preventmagnetic armature 635 from seizing to magnets 610 and/or magneticmaterial 630 by preventing physical contact between magnetic armature635 and the magnets 610 and/or magnetic material 630.

In the example of FIG. 6, control motor 600 also features springs 645that may allow the non-magnetic material 640 to move somewhat relativeto magnetic armature 635, magnets 610, and/or magnetic material 630.Teachings of certain embodiments recognize that allowing some movementby the non-magnetic material 640 separating magnetic armature 635 frommagnets 610 and/or magnetic material 630 may further reduce seizing bycontrol motor 600.

In the examples of FIGS. 3-6, the control motor includes a shaft thatmoves linearly in an effort to adjust the spool of a hydraulic system230. Teachings of certain embodiments recognize, however, the ability toprovide a rotary control motor that adjusts the spool of a hydraulicsystem 230.

FIG. 7A shows a control system 700 featuring a control motor 710, ahydraulic system 230, and an actuator 220. In the example of FIG. 7,control motor 710, hydraulic system 230, and actuator 220 may resemblethe motor 119, the dual concentric valve 102, and the parallel dualpiston actuator 111 of U.S. Pat. No. 7,828,245.

As seen in the example of FIG. 7, control motor 710 is a rotary controlmotor that adjusts the spool of hydraulic system 230 by rotating itsoutput shaft 715. A joint 720 converts rotation of the output shaft 715into linear movements of the spool of hydraulic system 230. Measurementdevices 730 measure rotation of the output shaft 715 and linear movementof the spool of hydraulic system 230. In one example embodiment,measurement devices 730 are differential transformers (e.g., linearvariable differential transformers).

FIG. 7B shows side view of joint 720, and FIG. 7C shows a cross-sectionend view of joint 720 according to one example embodiment. In theexample of FIGS. 7B and 7C, the spool of hydraulic system 230 featurestwo disks forming a trough 722 between them. A spherical member 724resides at least partially in trough 722. Output shaft 715 features adisk 725 that includes a recess sized to receive at least part ofspherical member 724. In operation, according to one example embodiment,rotation of output shaft 715 causes disk 725 to reposition sphericalmember 724. Repositioning spherical member 724 causes spherical member724 to apply force against one of the disks forming trough 722. Thisforce results in linear movement of the spool of hydraulic system 230.

In the example of FIGS. 7A-7C, however, control system 700 may fail ifjoint 720 jams. For example, jamming of joint 720 may lock the positionof the spool of hydraulic system 230 and thus prevent both controlmotors 710 from operating. Accordingly, teachings of certain embodimentsrecognize the capability to reduce failures of joint 720.

FIGS. 7D-7F show cross-section views of joint 720 according to oneexample embodiment. As seen in FIGS. 7D-7F, disk 725 features a pin 726,a detent member 727, and a spring 728. In this example, detent member727 is positioned between pin 726 and spring 728, and spring 728 appliesa force against detent member 727 towards pin 726. Pin 726 features adetent portion that is sized to receive at least a portion of detentmember 727 when the detent portion is facing detent member 727.

Spherical member 724 is positioned between trough 722 and pin 726.During normal operation, according to one example embodiment, disk 725repositions spherical member 724 without substantially moving pin 726.For example, spring 728 may apply sufficient force against pin 726 toprevent pin 726 from rotating during normal operation.

As friction increases in joint 720, however, spherical member 724 maycause pin 726 to rotate within disk 725. If the increased frictionpersists, pin 726 may continue to rotate until its detent portion facesdetent member 727. At this point, spring 728 may force detent member 727at least partially into the detent portion of pin 726, thus preventingpin 726 from rotating further.

In this example, joint 720 may continue to operate for some time withdetent member 727 forced into the detent portion of pin 726. Forcingdetent member 727 at least partially into the detent portion of pin 726,however, may represent visual evidence of increased friction in joint720. This visual evidence may be apparent, for example, during apreflight check of joint 720. Evidence of increased friction in joint720 may indicate that joint 720 is close to failing. Accordingly,teachings of certain embodiments recognize that providing visualevidence of increased friction may allow joint 720 to be repaired and/orreplaced prior to failure.

Thus, teachings of certain embodiments recognize the capability toreduce failures of joint 720. In addition, teachings of certainembodiments recognize the capability to reduce failures in controlmotors such as control motor 710.

FIGS. 8A and 8B show cross-section views of a control motor 800according to one example embodiment. In the example of FIGS. 8A and 8B,control motor 800 features magnets 810, coils 820, magnetic material830, non-magnetic material 840, and a shaft 850. In this example, coils820 may be considered static components, and magnet 810, magneticmaterial 830, and shaft 850 may be considered movable components.

In operation, magnets 810 generate magnetic flux along a magnetic fluxpath. Magnetic material 830 may reduce loss of flux along the magneticflux path. Coil 820 selectively adds magnetic flux to and/or subtractsmagnetic flux from the magnetic flux path. Adding or subtractingmagnetic flux may cause magnets 810 and magnetic material 830 to rotatewithin control motor 800. Shaft 850 is coupled to magnetic material 830and is configured to rotate with magnetic material 830.

Magnet 810 may represent any material or object that is operable toproduce a magnetic field and/or generate a magnetic flux path. Examplesof magnet 810 may include a permanent magnet or an electromagnetic. Coil820 may represent any material or object that is operable to add orremove flux to or from a magnetic flux path. In some embodiments, coil820 resembles a series of loops of conductive material, such as solidcopper wire. Magnetic material 830 may represent any material or objectthat is attracted to (or repulsed by) a magnet. In some embodiments,magnetic material 830 may include ferromagnetic materials, such as iron,nickel, cobalt, rare earth magnets, and some alloys. Non-magneticmaterial 840 may represent material is not attracted to (or repulsed by)a magnet. Examples of non-magnetic material 840 may include somerubbers, plastics, and wood. In the example of FIGS. 8A and 8B,non-magnetic material may hold magnets 810 against magnetic material930.

In the example of FIG. 8A, shaft 850 rotates within control motor 800.In some embodiments, bearings 860 may be provided to separate shaft 850from static components of control motor 800 and allow for rotation ofshaft 850 within control motor 800. Bearings 860 may fail duringoperation, however, and restrict rotation of shaft 850. Accordingly,teachings of certain embodiments recognize the capability to providebreak wires 865 proximate to bearings 860. Break wires 865 may detectfailure of a bearing 860 by severing in response to a failure of thebearing 860. Teachings of certain embodiments recognize that detectingfailure of bearing 860 may allow maintenance workers to replace thebearing 860 so as to prevent further damage and/or more catastrophicfailures.

In addition to bearing failure, control motor 800 may also be prone tofailure due to magnetic seizing. In the example of FIGS. 8A and 8B,magnets 810 and magnetic material 830 are disposed within control motor800 adjacent to coil 820. During normal operation, magnets 810 andmagnetic material 830 may be free to rotate within control motor 800adjacent to coil 820. A failure can occur, however, if magnets 810 ormagnetic material 830 seizes to coil 820. In this failure mode, magnets810 and magnetic material 830 become fixed and prevent shaft 850 fromrotating. Preventing shaft 850 from rotating may, in turn, prevent shaft850 from moving the spool of hydraulic system 230, which may result in afailure of the actuator 220 coupled to hydraulic system 230.Accordingly, as will be explained in greater detail below, teachings ofcertain embodiments recognize the capability to prevent failures ofactuator 220 and hydraulic system 230 by preventing magnetic seizing ofthe control motor.

FIGS. 9A and 9B show cross-section views of a control motor 900according to one example embodiment. In the example of FIGS. 9A and 9B,control motor 900 features magnets 910, coils 920, magnetic material930, non-magnetic material 940, and a shaft 950. In some embodiments,some of these components may resemble the magnets 810, coils 820,magnetic material 830, non-magnetic material 840, and shaft 850 ofcontrol motor 800. Unlike control motor 800, however, control motor 900features additional non-magnetic material 940 adjacent to coil 920 andseparating coil 920 from magnets 910 and magnetic material 930.Teachings of certain embodiments recognize that the additionalnon-magnetic material 940 may prevent coil 920 from seizing to magnets910 and/or magnetic material 930 by preventing physical contact betweencoil 920 and the magnets 910 and/or magnetic material 930.

FIGS. 10A and 10B show cross-section views of a control motor 900according to another example embodiment. In the example of FIGS. 10A and10B, control motor 1000 features magnets 1010, coils 1020, magneticmaterial 1030, non-magnetic material 1040, and a shaft 1050. In someembodiments, some of these components may resemble the magnets 810,coils 820, magnetic material 830, non-magnetic material 840, and shaft850 of control motor 800.

Unlike control motor 800, however, control motor 1000 featuresadditional non-magnetic material 1045 separating coil 1020 from magnets1010 and magnetic material 1030. In the example of FIGS. 10A and 10B,the additional non-magnetic material 1045 is at least partially movablerelative to both coil 1020 and the moving components of magnets 1010,magnetic material 1030, and shaft 1050. For example, in FIG. 10A,bearings 1046 allow the additional non-magnetic material 1045 to rotaterelative to shaft 1050 (i.e., shaft 1050 is free to rotate insidenon-magnetic material 1045 and/or non-magnetic material 1045 is free torotate about shaft 1050).

In addition, a spring 1047 couples the additional non-magnetic material1045 to the static portion of control motor 1000. In this example,spring 1047 allows the additional non-magnetic material 1045 to at leastpartially move relative to the static portion of control motor 1000. Inaddition, spring 1047 restricts (but does not completely prevent)rotation of non-magnetic material 1045 relative to shaft 1050.

Teachings of certain embodiments recognize that the additionalnon-magnetic material 1045 may prevent coil 1020 from seizing to magnets1010 and/or magnetic material 1030 by preventing physical contactbetween coil 1020 and the magnets 1010 and/or magnetic material 1030. Inaddition, allowing the additional non-magnetic material 1045 to moverelative to both the movable and static components of control motor 1000may further reduce seizing by control motor 1000 and may reduce frictionand wear within control motor 1000

In each of the example control motors 800, 900, and 1000, break wiresare provided to detect bearing failures. In each of these examples,break wires may detect failure of a bearing by severing in response to afailure of the bearing. Teachings of certain embodiments recognize,however, other mechanisms for detecting failure of a bearing.

FIGS. 11A and 11B show cross-section views of a control motor 1100according to one example embodiment. In the example of FIGS. 11A and11B, control motor 1100 features magnets 1110, coils 1120, magneticmaterial 1130, non-magnetic material 1140, and a shaft 1150. In someembodiments, some of these components may resemble the magnets 810,coils 820, magnetic material 830, non-magnetic material 840, and shaft850 of control motor 800.

Unlike control motor 800, however, control motor 1100 features a metaltube 1152 positioned around shaft 1150. In one example embodiment, metaltube 1152 is aluminum or an aluminum alloy. Control motor 1100 alsofeatures electrical transmission lines 1154 and 1154. In the example ofFIGS. 11A and 11B, electrical transmission line 1154 is associated withshaft 1150, and electrical transmission line 1156 is associated withtube 1152. In one example embodiment, electrical transmission lines 1154and 1156 are electrically coupled to shaft 1150 and tube 1152. Inanother example embodiment, electrical transmission lines 1154 and 1156are located adjacent to shaft 1150 and tube 1152.

Control motor 1100 also features jam members 1162 and 1172. Jam member1162 is located proximate to spherical member 1160. In one exampleembodiment, spherical member 1162 may resemble and/or operate similarlyto spherical member 724. Jam members 1172 are located proximate tobearings 1170 and secondary bearings 1171. In one example embodiment,bearings 1170 may resemble and/or operate similarly to bearings 860.Secondary bearings 1171 may act as backup bearings and engage inresponse to a failure by bearings 1170.

In operation, according to one example embodiment, elements such asspherical member 1160 and bearings 1170 may jam or otherwise fail. FIG.11A shows the position of jam members 1162 and 1172 prior to failure byspherical member 1160 and bearings 1170. As seen in FIG. 11B, failure byspherical member 1160 or a bearing 1170 may cause jam members 1162 and1172 to deform part of tube 1152. For example, a failure by one of thebearings 1170 may cause secondary bearings 1171 to engage, which causessecondary bearings 1171 to displace jam members 1172.

In the example of FIG. 11B, deforming tube 1152 relieves the jam andcauses tube 1152 to contact shaft 1150, thus completing an electricalcircuit between electrical transmission line 1154 and electricaltransmission line 1156. Completing the electrical circuit may alertmaintenance workers to a failure within control motor 1100 and may allowmaintenance workers to perform repairs so as to prevent further damageand/or more catastrophic failures. In addition, deforming tube 1152 mayrelieve the jam by spherical member 1160 and/or bearings 1170 andtherefore allow control motor 1100 to continue operating until repairscan be made.

FIGS. 12A-12C show cross-section views of a control motor 1200 accordingto another example embodiment. In the example of FIGS. 12A and 12B,control motor 1200 features magnets 1210, coils 1220, magnetic material1230, non-magnetic material 1240, a shaft 1250, a spherical member 1260,bearings 1270, and secondary bearings 1271. In some embodiments, some ofthese components may resemble the magnets 1110, coils 1120, magneticmaterial 1130, non-magnetic material 1140, shaft 1150, spherical member1160, bearings 1170, and secondary bearings 1171 of control motor 1100.

Unlike control motor 1100, however, control motor 1200 featuresresettable ball detents 1172 and springs 1274. FIG. 12A shows thepositions of ball detents 1272 prior to failure by bearings 1270. Asseen in FIG. 12A, spring 1274 forces ball detents 1172 against secondarybearings 1271.

FIGS. 12B and 12C show the positions of ball detents 1272 after failureby bearings 1270. In these examples, failure of bearings 1270 causessecondary bearings 1271 to force ball detents 1272 back against spring1274. Forcing ball detents 1272 back against spring 1274 pulls detentpin 1252 downwards and closes the electrical circuit between electricaltransmission line 1254 and electrical transmission line 1256.

In some embodiments, ball detents 1272 may be reset after the bearingjam is repaired. For example, after bearings 1270 and/or secondarybearings 1271 are reset/repaired/replaced, detent pin 1252 may be pulledupwards, and spring 1274 may force ball detents 1272 into the originalposition. Teachings of certain embodiments recognize that providingresettable ball detents may reduce the time and expense necessary torepair a bearing jam.

Modifications, additions, or omissions may be made to the systems andapparatuses described herein without departing from the scope of theinvention. The components of the systems and apparatuses may beintegrated or separated. Moreover, the operations of the systems andapparatuses may be performed by more, fewer, or other components. Themethods may include more, fewer, or other steps. Additionally, steps maybe performed in any suitable order.

Although several embodiments have been illustrated and described indetail, it will be recognized that substitutions and alterations arepossible without departing from the spirit and scope of the presentinvention, as defined by the appended claims.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims to invokeparagraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereofunless the words “means for” or “step for” are explicitly used in theparticular claim.

What is claimed is:
 1. A rotorcraft, comprising: a body; a power traincoupled to the body and comprising a power source and a drive shaftcoupled to the power source; a hub coupled to the drive shaft; a rotorblade coupled to the hub; a hydraulic actuator in mechanicalcommunication with the rotor blade and operable to change a position ofthe rotor blade; an actuator control valve system operable to regulate aflow of fluid to the hydraulic actuator; and a linear control motor inmechanical communication with the actuator control valve system, thelinear control motor comprising: a first permanent magnet operable togenerate a first magnetic flux path; a coil operable to selectively addmagnetic flux to and subtract magnetic flux from the magnetic fluxflowing in the first magnetic flux path; a first magnetic materialdisposed at least partially in the first magnetic flux path; a staticcomponent comprising at least one of the first permanent magnet, thecoil, and the first magnetic material; a movable component operable tomove relative to the static component in response to variations in fluxflowing in the first magnetic flux path, the movable componentcomprising at least one of the first permanent magnet, the coil, and thefirst magnetic material, the static component and the movable componentbeing different components; a shaft in mechanical communication with theactuator control valve system and coupled to the movable component suchthat the shaft is operable to move linearly in response to variations influx flowing in the first magnetic flux path; a first non-magneticmaterial disposed between the movable component and the static componentand operable to prevent physical contact between the movable componentand the static component; and a spring in mechanical communication withthe first non-magnetic material, the spring configured to allow thefirst non-magnetic material to move relative to the moveable componentand the static component.
 2. The rotorcraft of claim 1, the actuatorcontrol valve system further comprising: a servo valve; and a spoolextending through the servo valve.
 3. The rotorcraft of claim 2, whereinthe shaft is directly coupled to the spool opposite the movablecomponent.
 4. The rotorcraft of claim 1, wherein the movable componentcomprises the coil.
 5. The rotorcraft of claim 4, wherein the coil is atleast partially disposed in the first magnetic flux path.
 6. Therotorcraft of claim 4, the linear control motor further comprising asecond magnetic material disposed at least partially in the firstmagnetic flux path and at least partially outside the coil.
 7. Therotorcraft of claim 1, the linear control motor further comprising asecond non-magnetic material disposed between the movable component andthe static component.
 8. A linear control motor, comprising: a firstpermanent magnet operable to generate a first magnetic flux path; a coiloperable to selectively add magnetic flux to and subtract magnetic fluxfrom the magnetic flux flowing in the first magnetic flux path; a firstmagnetic material disposed at least partially in the first magnetic fluxpath; a static component comprising at least one of the first permanentmagnet, the coil, and the first magnetic material; a movable componentoperable to move relative to the static component in response tovariations in flux flowing in the first magnetic flux path, the movablecomponent comprising at least one of the first permanent magnet, thecoil, and the first magnetic material, the static component and themovable component being different components; a shaft coupled to themovable component such that the shaft is operable to move linearly inresponse to variations in flux flowing in the first magnetic flux path;a first non-magnetic material disposed between the movable component andthe static component and operable to prevent physical contact betweenthe movable component and the static component; and a spring inmechanical communication with the first non-magnetic material, thespring configured to allow the first non-magnetic material to moverelative to the moveable component and the static component.
 9. Thelinear control motor of claim 8, wherein the movable component comprisesthe coil.
 10. The linear control motor of claim 9, wherein the coil isat least partially disposed in the first magnetic flux path.
 11. Thelinear control motor of claim 9, further comprising a second magneticmaterial disposed at least partially in the first magnetic flux path andat least partially outside the coil.
 12. The linear control motor ofclaim 8, wherein the movable component comprises the first magneticmaterial.
 13. The linear control motor of claim 8, further comprising asecond permanent magnet operable to generate a second magnetic fluxpath, the movable component operable to move relative to the staticcomponent in response to variations in flux flowing in the first andsecond magnetic flux paths.
 14. The linear control motor of claim 13,wherein the first magnetic flux path is operable to move the movablecomponent in a first direction and the second magnetic flux path isoperable to move the movable component in an opposite second direction.15. The linear control motor of claim 13, wherein the coil is operableto selectively add magnetic flux to the magnetic flux flowing in thefirst magnetic flux path or remove magnetic flux from the magnetic fluxflowing in the second flux magnetic flux path such that the coil causesthe movable component to move in a direction of stronger magnetic flux.16. The linear control motor of claim 8, further comprising a secondnon-magnetic material disposed between the movable component and thestatic component.